What do you do when your bestfriend haves with the guy your dating?

I've been friends with this girl for five years and i've been dating this guy for a couple of months. I introduced her to him on my prom night and after that they became friends. Later on my bestfriend told me they had . She thought it wasn't a big deal, because me and him wasn't that serious. He told me he was sorry, because he knew he was wrong and didn't think it would go as far. I'm not mad anymore that they had . I'm mad, because she still hasn't apologize and hasn't called me since and it's been two months. Should i call and confront her or just let the friendship go?